In a Japan regularly attacked by kaiju, Kafka Hibino works for a cleanup crew responsible for removing the remains of these creatures after the Defense Force has defeated them. He once dreamed of fighting alongside them but gave up that ambition long ago. After a mysterious incident, however, Kafka gains the ability to transform into a kaiju while retaining his human consciousness. Now torn between his desire to join the Defense Force and the need to hide his true nature, he tries to protect others while facing increasingly dangerous creatures.